This invention relates to a window winder for a slidable window, especially a window which can be lowered into the window shaft of an automobile, comprising a threaded cable displaceable in tension-resistant and compression-resistant manner in a guide tube, with which cable there is in engagement, in a two-part drive casing, the drive pinion non-rotatably keyed to a drive shaft journalled in the two casing halves of a gear wheel drive equipped with a drag spring brake, and which cable is directly or indirectly connected to the window by one or more entraining devices secured to the threaded cable and penetrating through a longitudinal slit in the guide tube, wherein the guide tube is a slit metal tube only approximately in the region of the path of movement of the entraining devices and elsewhere is a plastics tube connected non-rotatably and non-displaceably to the drive casing and metal tube by means of sleeves injection moulded onto the plastics tube.
In a known window winder of this type of construction (DE-PS No. 19 31 472), in which the plastics tube is manufactured from a relatively stiff plastics material bent if necessary using heat into the predetermined bending radii, such as copolymerized polyacetals, the plastics tube is conducted through the drive casing and is furnished at the position of its passage with an aperture for the penetration of the drive pinion. The drive casing here consists as usual (DE-PS No. 11 98 239) of two sheet steel components, which surround the tube passing through the casing with a tube profile half formed in each of these two parts and are riveted together. The sheet steel casing is secured against axial displacement by two sleeves injection moulded onto the plastics tube on either side of the integrally formed tube profile, additional closely fitting clamping devices between the sleeves and the drive casing securing against rotation. The aperture for the passing of the drive pinion is, in this known window winder, milled in the shape of a circular arc into the plastics tube to suit the external diameter of the pinion.
This known window winder is indeed functionally relaible, but its economic manufacture presents considerable difficulties. Thus, the injecting around of the plastics tube with two sleeves, the distance of which from one another must equal the width of the drive casing within close tolerances, has proved extremely difficult. In addition, excess injected material on the sleeves must be removed by hand in a time-consuming manner before the tube is placed in. The arc-shaped, milled aperture not only leads to a considerable weakening of the tube cross-section in this region but also necessitates subsequent deburring by hand. A very substantial disadvantage of the known window winder results from the variation within wide tolerances of the wall thickness of the plastics tube, which has a very adverse effect in the region of the pinion penetration upon the axial distance between pinion and threaded cable which must be maintained in the interest of optimum tooth engagement between pinion and threaded cable.
The task underlying the present invention is, while avoiding the aforementioned disadvantages, to propose a window winder which can be manufactured economically to accurate dimensions, and which in particular does not need to be finished by hand at the state points, and which permits an exact maintaining of the axial distance between the drive pinion and threaded cable.
Starting from a window winder of the category initially named, the invention solves this task by the fact that the two parts of the drive casing are injection moulded from plastics material and that their parting plane is situated outside the threaded cable passing through the casing and outside the drive pinion between the drive pinion and the drag spring brake, a guide duct guiding the threaded cable and substantially aligned with the inner surface of the guide tube and open towards the drive pinion and towards the parting plane being disposed in one part of the casing, and by the fact that, of the sleeves situated on the casing, each is formed on and therefore formed in one piece with one casing part.
In the window winder constructed according to this invention, the plastics tube is no longer conducted through the casing , so that not only the milling of an aperture in the plastics tube for passage of the pinion is eliminated, but also fluctuations in the wall thickness of the plastics tube do not have any influence upon the axial spacing between pinion and threaded cable. The aforementioned axial distance is always exactly maintained by the defined position of the guided duct in the one casing part predetermined by the injection mould. The aforementioned special position of the dividing plane of the casing ensures that the two casing parts are not forced apart by the pressure acting on the cable due to engagement of the teeth. The forces acting transversely upon the cable are directly accepted by the guide duct wall, which is substantially curved in correspondence with the internal surface of the adjoined guide tube, without casing deformations arising and without the ends of the casing parts being loaded. Since the guide duct extends across the full width of the drive casing, a sufficiently large bearing surface is also available to the cable in the drive casing, so that there is no risk of premature wear. The favourable coefficient of friction between the material of the cable and the plastics casing moreover leads to especially easy running in the vicinity of the drive. The injection moulding of the casing parts moreover offers the advantage that the sleeves which form the connection to the plastics tube can be formed in one piece with the casing parts, so that requirements for subsequent finishing in the region of the sleeves are completely eliminated. The distance between the sleeves determined by the injection mould is no longer decisive for the fitting of the casing to the plastics tube, because the plastics tube is no longer conducted through the casing.
The arrangement is preferably such that the parting plane through the drive casing is approxiamtely tangential to the external periphery of the threaded cable, and that the guide duct is formed back-cut relative to the parting plane. By the back-cut, the bearing and guide surface of the duct guiding the threaded cable is still further increased. In addition, the region of the guide duct resulting from the back-cut takes account of the circumstance that the compression forces exerted by the guide pinion upon the threaded cable acts not only tangentially but also, due to the helical shape of the winding on the threaded cable, cause a component of force transversely to the parting plane of the casing. This component of force is accepted by the region of the duct formed by the back-cut without any effect upon the holding-together of the two fixed together parts of the casing.
The part of the casing opposite to the guide duct for the threaded cable is equipped with a pot-like formation for housing the drag spring brake typical of this drive system. Here, the drag spring can bear directly against an inner cylindrical wall surface of the pot-like formation. It has been found that, in spite of the frictional pair between the steel of the drag spring and the plastics of the casing, an absolutely sufficient brake action is achieved against the reverse forces introduced by the threaded cable. To prevent the turns of the drag spring from penetrating into the plastics cylinder wall, the arrangement may with advantage be such that a metal cylinder surrounding the drag spring is pressed in or moulded in to the part of the casing which houses the drag spring, coaxially to the drive shaft.
In order to attain exact alignment between the two parts of the casing in respect of the bearing positions for the drive shaft and of the sleeves opposite to the casing, it is of advantage of centering pins or the like are moulded onto one casing part at the parting plane and perpendicularly thereto, depressions in the opposite casing part corresponding to these pins.
The two parts of the casing can be firmly connected together by conventional detachable or permanent connecting elements, for example by screws or rivets. A substantial saving in time in assembly of the casing can , however, be achieved if, for the purpose of connecting the two casing parts together, connecting elements which engage with and interlock with one another on assembly are intergrally formed on the two housing parts. Such connecting elements come automatically in operation when the two parts of the casing are pressed together guided by the centering pins.
The two casing parts, the plastics tube and the sleeve provided for the connection to the slit metal tube can be made from the same stiff thermoplastics material, preferably from polyacetal. The plastics tube attached to the casing as the outlet tube for the free end of the threaded cable may, by contrast, be made from hard polyethylene, because due to the flexibility of this material automatic adapting of the outlet tube to the existing internal space of the window shaft is rendered possible. An elastically flexible plastics tube can with advantage be provided also between the slit metal tube and the drive casing. Such an elastically flexible plastics tube offers the advantage that the window winder does not have to be adapted from the start by a suitably curved guide tube to the installation situation in the automobile. When an elastically flexible plastics tube is used, this tube can remain in the straight position during manufacture, storage and transporting and does not need to be bent until installation in the automobile. Such a plastics tube is capable also of taking up considerable dimensional deviations at the place of installation. For an elastically flexible plastics tube, suitable materials in particular are polyamide 12 and polytetramethylene terephthalate. These plastics materials on the one hand are sufficiently flexible when formed into tubes, but on the other hand possess sufficient stability of shape for the guide tube formed from them not to become deformed when the window winder is operated as a result of the forces transmitted by the threaded cable.
In order to provide a firm anchorage for the plastics tube to the drive casing, it is advantageous if the ends of the plastics tube, which are injected around with sleeves during the injection moulding of the casing parts and which adjoin the casing parts, are mechanically connected to the casing in known manner by transverse milled recesses at the outer periphery of the plastics tube and/or holes through this tube.
In order to achieve an exact guiding of the threaded cable in the guide duct in the region of the pinion, the arrangement is with advantage such that the guide duct is reduced in radius in the region of the drive pinion to the external diameter of the threaded cable.
Further details of the invention are explained in more detail below with reference to the drawings illustrating an example of embodiment thereof.